The "Formel E" badge on the boot refers to the engine/drivetrain. I suppose in the '70s and '80s they were on an economy drive and they equipped the Formel E cars with high compression 1.1 carburettor engines and an overdrive fourth gear in an effort to maximise the fuel economy. I think they got low rolling esistance tyres too. You did have to use higher octane 98RON fuel though to get the fuel economy but since that was more expensive than ordinary 95RON petrol I can't see too many miserable bachelor farmers splashing out on the premium juice.
They also put a fuel economy gauge in the dash clocks. It wasn't an exact science, it was run off inlet manifold vacuum so depending on how far open the throttle butterfly was, the vacuum was greater or less and moved the needle on the dash. As for the trim level, the Formel E Derby didn't come with bog standard "S" spec (no chrome trim, one sun visor) but it came with the "LS" spec (chrome side trim, chrome trim in the window rubbers, TWO sun visors !!!, still no headrests in the seats though).
I presume something similar applied to the Formel E golfs. From what I can gather, the UK didn't get Formel E mk1 Polos/Derbys. They waited til the mk2 Polo/Polo Saloon came in to introduce the Formel E spec.